Data communication in automotive vehicles sometimes takes the form of a controller area network (CAN) which was developed for factory operations. The CAN bus is a differential serial data communication bus using a twisted pair of lines respectively carrying high signal (CANH) and a low signal (CANL). Data is self synchronizing because of it's variable pulse width protocol. The bus has two states: a recessive bit where there is a 0 VDC differential between CANH and CANL, and a dominant bit where there is a 2 VDC differential. The CAN International Standard (ISO 11898) has provisions for only controlled slew rates for both outputs. There is no phasing requirements for CANH and CANL with respect to each other.
Although CAN is useful for vehicle applications it produces an objectionable level of radiated emissions. To minimize radiated emissions during high speed transmissions, the phase of the signals must be kept as close to zero as possible, i.e. CANH+CANL equal a constant DC voltage.